This project presents the modeling and simulation of two key spacecraft subsystems:
- An active thermal control system based on deployable radiators
- A simplified Attitude Control System (ACS) for drag compensation
The work combines multi-domain physical modeling (thermal, mechanical, electrical) and control design, implemented using both causal (Matlab) and acausal (Modelica/Simscape) approaches.
The satellite thermal model is based on a lumped parameter approach with five nodes:
- Main body
- Two solar panels
- Two deployable radiators
Key features:
- Radiator emissivity varies with rotation angle
- Heat exchange includes:
- Solar radiation
- Deep space radiation
- Conductive coupling between nodes
- Temperature regulation achieved through active control of radiator angle
- DC motor-driven hinge mechanism
- Electromechanical coupling:
- Electrical circuit (R–L–back EMF)
- Mechanical rotation dynamics
- Control input: proportional law based on body temperature
A simplified ACS is designed to compensate atmospheric drag:
Subsystems:
- Accelerometer (mass-spring-damper model)
- Voltage modulation (operational amplifier)
- Solenoidal valve (electromagnetic actuator)
- Ion thruster (mass flow → thrust generation)
The system dynamically adjusts thrust to match time-varying drag disturbances.
- Full nonlinear ODE system derived for both subsystems
- Multi-domain coupling:
- Thermal
- Mechanical
- Electrical
- Stiff system solved using
ode15s - Control strategies:
- Constant proportional gain
- Adaptive gain tuning
- Parameter tuning for:
- Thermal stability
- Drag-thrust matching
Two environments were used:
- Block-based multi-physics modeling
- Custom components for:
- Variable emissivity
- Control logic
- Validation against Matlab results
- Physical modeling using:
- Mechanical translational components
- Electrical circuits
- Solenoid actuator
- Hybrid approach with embedded analytical models (thruster, drag)
- Stable regulation around target temperature (294.15 K)
- Oscillations reduced below 0.1% within required time
- Radiator angle converges to equilibrium configuration
- Strong agreement between causal and acausal models
- Effective compensation of atmospheric drag
- Steady-state thrust error on the order of 10⁻⁶ N
- Fast transient response (~15 s)
- Sensitivity to initial conditions highlighted
- Matlab (causal) and Modelica results are nearly identical
- Simscape model shows small discrepancies due to:
- Solenoid modeling differences
- Sensitivity to parameters
The project includes:
- Nonlinear ODE formulation of multi-domain systems
- Numerical integration of stiff dynamics
- Control system design and tuning
- Modelica and Simscape implementations
- Comparative validation between modeling approaches
- Lumped thermal modeling
- Radiative heat transfer
- Electromechanical systems
- DC motor dynamics
- Mass-spring-damper systems
- Ion propulsion modeling
- Stiff ODE systems
- Causal vs acausal modeling
Matteo Portantiolo
MSc Space Engineering – GNC